In many areas there are substantial slopes and grade changes on the land surfaces. These slopes and grade changes pose problems for agricultural implements and other equipment which move over or are positioned on such grades. The grade changes experienced by implements moving thereon make optimal positioning of the implement and any header or tool carried on the implement more difficult to achieve.
One type of implement which in particular experiences such problems with sloped hillsides are combine harvesters. Combine harvesters have relatively high centers of gravity and variable amounts of weight contained in a grain bin which receives the cut and threshed grain. The high center of gravity and variable weight distribution make negotiating hillsides of varying slope difficult and dangerous in some instances.
In some leveling hillside combine harvesters each side of the main or front wheels are operated up and down in a range of positions which maintain the large wheels at each side in a vertical or near-vertical position over the full range of vertical adjustment. This works well when there are single wheels at each side. However, when dual wheels are used at each side, then leveling a combine on a hillside will cause contact to be made with the ground less even and can cause only one wheel of each dual wheel set to always be in ground contact at each side of the implement. Thus, the reasons and advantages for having dual wheels are in some cases rendered less effective.
One approach uses a continuous front axle construction having a central pivot at or near the center of the axle. This construction places all of the weight carried by the front axle onto a single pivot located at the midpoint of the axle. Placing all the front axle weight of a loaded combine onto a single pivot creates a mechanically demanding situation for both the pivot and axle. Placing all the weight at the midpoint of the axle creates greater loading of the axle. The midpoint position typically develops the largest bending moment in the axle and with the main load centered thereon, then this problem is exacerbated. Accordingly, the axle must be built strong in order to carry this midpoint loading of the entire weight carried by the front axle. This in turn causes the front axle to have increased weight and costs of production.
Center pivot hillside leveling combines also have required the implement body to be positioned relatively high to allow adequate tire clearance when the wheels move up relative to the body. This places the center of gravity of the implement higher and this is not as preferred as a lower center of gravity.
Many prior hillside leveling machines also have a very high center of gravity. This high center of gravity exacerbates potential instability. It also increases the height differential which must be accommodated between the main part of the combine and the feeder which takes the output from the header and feeds it into the main part of the combine for threshing. The header contains the gathering reel, cutting bars and augers that move the cuttings toward the feeder. Earlier combines having two independent front axles also experience more fluctuation in this differential height between the feeder and main part of the combine.
Given these demanding design criteria it has typically been necessary to have substantially different designs for hillside combines as compared to flatland combines. Differences typically include changing the location of the front axle so that it moves further forward. This change increases the distance between the front and back wheels and increases the turning radius of the combine and making maneuvering more difficult on an implement already difficult to maneuver. It also changes the weight distribution between the wheels which may have an adverse effect on leveling and the maximum grade which can be handled by the combine.
It has also been difficult for hillside combines to adequately provide both optimal leveling of the main body and tilt angle adjustment for the header and feeder assemblies or other tool carried which must be adjustably angled for optimal performance.
The differences in design between flatland combines and hillside combines increase engineering, manufacturing and inventory costs for the manufacturer and the dealers selling the machines.
Thus, there has been a long-felt need for improved tilting hillside combines and other machines which are in need of tilt adjustments for the varying slope of terrain over which they travel and are situated. The current invention addresses one or more of the indicated deficiencies experienced by the prior art.